The enormous diversity and specificity of individual neurons within the central nervous system (CNS) arise during neurogenesis as an undifferentiated epithelial sheet is transformed into a highly differentiated CNS. How the correct numbers and types of neurons are assembled at the right time and place during development to generate a properly functioning CNS is the topic of this grant. Here we propose to use the powerful molecular genetics of Drosophila to study the molecular mechanisms controlling neurogenesis during embryonic development. We propose to study the expression and function of three genes which we have previously shown to be involved in these events: S8, fushi tarazu (ftz), and punt. The S8 gene appears to control the specification of a specific region of the CNS. The fushi tarazu gene (a homeobox segmentation gene encoding a nuclear regulatory protein) is transiently expressed a second time during neurogenesis as a putative control of neuronal fate in the CNS. The punt gene appears to control the number of cell divisions of neuronal precursor cells in particular regions of the CNS. The molecular genetic studies proposed here will help us better understand how genes control the specification of particular region of the CNS, the specification of particular neuronal precursor cells and neuronal generated in particular regions. In so doing, these studies will aid in our understanding of both the normal and abnormal development of the human brain and behavior, and potentially help us better understand certain types of abnormal mental health and disease.